Hi, I want realize (for hobby) a indoor led christmas lights. All leds shoud be series connected, but i've seen led drivers for 10led (no more)...for 100leds, 10 led drivers can be avoided? how can i connect all these lights? Any suggestion? Thanks in advance
A word of warning on the capacitor: It should have an AC voltage rating. I have had capacitors fail as ballasts with peak voltage of the AC less than the DC rating of the capacitor. The capacitor usually went POP or BANG when it failed.
I have had 250 volts AC blow two oil filled capacitors with 600 volt DC ratings and no AC ratings, as well as one foil / waxed paper capacitor with an 800 volt DC rating and no AC rating. One of the oil filled ones left a large oil stain on the ceiling, a misting of oil on nearby objects, and oily capacitor guts on the floor nearby in the process. I also once had some sort of poly cap with a 600 volt DC rating and no AC rating fail loudly from 240 or 250 volts AC.
All of these occurred during a 2 week period of my more reckless youth, towards the end of which had any BANG being followed by my mother or one of my brothers asking "capacitor?".
Whenever I saw a capacitor with both DC and AC voltage ratings (always after those adventurous two weeks), the AC voltage rating was always a lot less than 70.7% of the DC one, usually 1/3 to 1/2. In addition, some dielectrics heat up more than others do with AC.
The problem is the temperature dependance of the forward voltage drop. The outside temperature as well as the internally generated heat will alter the voltage drop and hence greatly affect the current.
While there may be flash lights in which the LED is directly connected to the batteries, but the internal resistance of the battery will function as a current regulator, so this is not a "constant voltage" source.
THe V-I curve is not only exponential, but it has a tempco that will put them into thermal runaway. The Chinese throwaway flashlights get away with it because of the internal resistance of the battery.
Have always been a bit concerned about the safety of tree lights and run them through an isolation transformer, irrespective of type. Also, the incandescent ones run for years if you reduce the rated voltage by around 10 or 20%...